Telephone-transmitter



` No. r149,448. EATENTED JAN. 12, 19o-4.

f P..G.VEANDALL. TELEPHONE TRANSMITTER.

Y AEPLIGATION FILED TEB.9, 1903. No. MODEL.

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Patented January 12, 1904.

PHILIP G. RANDALL, OF BOSTON, MASSACHUSETTS.

TELEPHONE-TRANSNHTTER.

SPECIFICATION forming part of Letters Patent No. 749,448, dated January12, 1904.

u Application iled February 9, 1903. Serial No. 142,526. (No model.)

To @ZZ whom. t may concern:

` Be itknown that I, PHILIP G. RANDALL, of Boston, in the county ofSuffolk and State of Massachusetts, have invented certain new and iusefullmprovements in Telephone-Transmitters, of which the following isa specification.

\ "This invention relates to telephone-transi y mitters; and itsprincipal object is to allow a stronger current to be sent through thein- I Q strument, thus increasing its power and ability to operate longand diH-icult circuits or a number oi' distinct circuits.

Other incidental objects accomplished are i. an increase in theVsensitiveness of the instrui5 tained therethrough.

Of the accompanying drawings, Figure 1 represents a vertical transversesection ot' a transmitter constructed in accordance with zo myinvention, the circuit connections being omitted. Fig. 2 represents arear elevation of the instrument with the back cover thrown down toexpose the interior. Fig. 3 represents a detail section showing theelectrode construction. Fig. 4. represents a diagrammatic view of onearrangement of circuits. Fig. 5 represents a similar view showinganother arrangementof circuits. Fig. 6 represents a similar view showinga third arrangement of circuits.

The same reference characters indicate the same parts in all thefigures.

\ In the drawings I have shown, for the purl i 1 Spese of illustratingmy invention, one oi the several structural forms which the body of ilthe instrument may assume and which, as shown, comprises a casingincluding an annular support 10, mounted in an upright position upon abase or standard 11 and having hinged thereto at 12 13 a front cover 14,in which a mouthpiece or concentrator 16 is 1 fixed, and a back `cover17, said covers being secured in normal position by spring-catches 1819. In `the center of the annulus 10, suspended by a plurality of pairsor groups of springs 20 20, is a plate, diaphragm, or pri- Mmarysound-receiver made oi' such a material and thickness as to be in itselfcomparatively stii or unbending and preferably made of a conductivematerial. Each group of springs,

ment and the distinctness of articulation obi as shown, consists oi' twosprings pressing on opposite sides oi' the diaphragm 21. The material ofthe diaphragm may permissibly be carbon, which would render thediaphragm suitable to act in different portions as an electrode orelectrodes operating in conjunction with spring-supported electrodes,such as those presently to be described.

22 22 are electrode-springs supported by their outer ends on the annulus10 and converging or radiating toward a center, their ends, as shown,being arranged in pairs on opposite sides of the diaphragm 21,four ofsuch pairs being illustrated. The number of electrodes cooperating withthe diaphragm may be more or less than the number here shown. Theelectrodes or resistance-contacts at the ends of the springs may be ofany desired material suitable to produce a marked variation inresistance of an electric circuit including such electrodes when thepressure against the electrodes is increased or diminished by thevibratory movements of the diaphragm. A suitable construction is shownin detail in Fig. 3, in which an electrode-disk 23, of carbon, issecured to the end of the spring 22, and in a cell between the disk 23and diaphragm 21 is placed a small body of loose granularresistance-varying material 24, such as carbon. The .side walls of thecell are formed by an annulus 25 oi' a yielding material, such as felt.Any other well-known form of resistance-varying unit may be employed, asmy invention does not reside in the particular construction of theelectrodes, contacts, or resistance-varying devices. Theresistance-varying points are not necessarily placed opposite eachother, but are so shown for the sake of convenience and symmetry. It isevident that when sound-waves are sent through the mouthpiece 16 ontothe diaphragm 21 the waves will vibrate said diaphragm as a whole inparallelism to itseli` and cause the electrical resistance between saiddiaphragm and the electrode-springs 22 to increase and diminishalternately on opposite sides of said diaphragm.

With the above construction of diaphragm and electrodes variousarrangements of circuits may be employed. In Fig. 4 I have shownelectrode-springs arranged in parallel IOO and adapted to transmitcurrents of alternating or opposite polarity to the line in obedience tothe vibrations of the diaphragm.

26 is the conventional induction-coil with secondary 27 included in theline 28 29.

30 31 are two batteries or two sections of a battery having a commonconnection by a wire 32 through the primary 33 of the induction-coil tothe transmitter diaphragm 21. The left-hand electrode-springs 22 areconnected through wires 34 35 with the positive pole of battery 31 andthe right-hand springs through wires 36 37 with the negative pole ofbattery 30.

The operation of the device with circuit connections'arranged as in Fig.4 is as follows: Assuming a movement of the diaphragm 21 to the right,which will increase resistance between it and the left-handelectrode-springs 22 and diminish resistance between it and theright-hand electrode-springs, a current begins to flow from the positivepole of battery 30 through the induction-coil primary 33, wire 32,diaphragm 21, and in parallel through the right-hand electrode-springs22 and wires 36 37 back to the negative pole of said battery. As soon asthe diaphragm moves in the opposite direction the current then finds itspath of least resistance through the left-hand electrode-springs, andaccordingly flows from the positive pole of battery 31 through wires 34in parallel through the left-hand electrodesprings 22, through thediaphragm 21, and through wire 32 and primary 33 back to the negativepole of the battery. In this case the current fiows through the primaryin the opposite direction from what it did before, so that a series ofalternating impulses are produced in the primary by the vibrations ofthe diaphragm.

In Fig. 5 I have shown an arrangement in which the pairs ofelectrode-springs are arranged in independent circuits. I show fourbatteries or battery-sections 3839 40 41, and the said batteries have,respectively, common connections through wires 42 43, the primaries 4445 of two induction-coils 46 47, and a wire 48 with the diaphragm 21.Wires 49 50 lead from the positive poles of batteries 38 40 to theleft-hand springs 22 22, and wires 51 52 lead from the negative poles ofbatteries 39 4() to the right-hand springs 22 22. By this arrangementeach pair of springs sends alternating impulses through its primary 44or 45 in the same Vmanner as I have described in connection with Fig. 4.rlhe secondaries 53 54 of the coils are shown as connected in parallelwith the line 28 29, so that the several sets of electrode-springsactuate the same line-circuit; but by keeping the secondaries 53 54separate the one instrument would obviously supply as many line-circuitsas there are secondaries and pairs of electrodes.

In Fig. 6 I have shown an arrangement for transmitting unidirectioncurrents through a primary circuit as in an ordinary transmitter. Abattery 55 is connected by wires 56 57 58 59 6() in parallel with all ofthe springs 22, and the diaphragm 21 is connected by a return-wire 61through the primary 33 of the induction-coil with the opposite side ofthe battery.

Various other plans of connections in addition to the foregoing might beemployed, as it will be understood that I have not attempted to give allthe possible arrangements. By mounting a comparatively stiff 0runbending diaphragm in a flexible support, so as to move in parallelismwith itself, I allow the soundwaves to have substantially the sameeffect throughout the whole area of the diaphragm, all of theresistance-varying units being affected in equal degree by each wave, nomatter what their position on the diaphragm. This enables me to employ alarge number of electrodes or resistance-varying units, if desired, andthus send a greater strength of current than heretofore through a singleinstrument. The construction shown in Figs. 1 and 2 allows either orboth sides of the sound-affected mechanism within the interior of theinstrument to be reached for inspection, adjustment, or repair byswinging down the corresponding cover 14 or 17, said covers closingopenings in the annular body 10 inclusive of the whole limits of saidsound-affected mechanism.

I claim-- 1. In a telephone-transmitter, a comparatively stiif orunbending vibrator or diaphragm, a plurality of groups of springsyieldingly supporting the same at different points around its margin andeach comprising springs pressing against opposite sides of saiddiaphragm, and a plurality of electrodes forming parts of differentresistance-varying units cooperating with said diaphragm.

2. In a telephone-transmitter, a comparatively stiif or unyieldingvibrator or diaphragm of electricallyconductive material constitutingthe primary sound-receiver and yieldingly mounted to vibrate inparallelism with itself, and a plurality of different resistance-varyingunits located on each side of said diaphragm, said units utilizing thematerial of the diaphragm as an electrical return.

In testimony whereof I have affixed my signature in presence of twowitnesses.

PHILIP G. RANDALL.

Witnesses:

R. M. PIERsoN, A. C. RATIGAN.

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